Patent GB-506433-A (GB)
Title: Improvements in the manufacture and production of hard solders
IPC: B23K35/30
Filed: 1937-12-20
Abstract: 506,433. Making metal powder. POWELL, A. R., and JOHNSON, MATTHEY, & CO. Ltd. Dec. 20, 1937, No. 35274. [Classes 83 (ii) and 83 (iv)] Soldering.-In a process for obtaining fine powders of such hard brazing solders as are normally sufficiently malleable to prevent their being converted into powders by mechanical grinding processes, the components are first divided into two portions, of which one portion comprises components which are such as to form a brittle alloy, and the other comprises a single malleable metal or mixture of metals which are such as to form a malleable alloy, then the components of the first portion are alloyed and reduced to powder mechanically as by grinding, then a fine powder of the second component obtained by suitable means, such as by the process described in Specification 506,432, is added thereto and the two powders finally mixed. Such solders may consist of a combination of copper and/or silver and/or gold with zinc and/or cadmium and/or tin and/or phosphorus. For precious metals platinum and/or palladium may also be employed. To produce a fine powder containing 50 parts silver, 15À5 parts copper, 16À5 parts zinc and 18 parts cadmium, a mixture of 15À5 parts copper, 16À5 parts zinc, 18 parts cadmium and 0-10 parts silver is melted to form a brittle alloy, which is then granulated by pouring into water; the granules broken by a stamping process and ground in a ball or other mill, preferably in a wet state. A fine powder of silver is added during grinding. The wet powder is washed and a small amount of acid may be added to produce flocculation and impurities are washed away by elutriation. The powder is then washed free from acid and dried. For preparation of a powder comprising 43 parts silver, 37 parts copper and 20 parts zinc, a brittle alloy of 16 parts copper and 20 parts zinc is formed and powdered as previously described and a malleable alloy of 43 parts silver and 21 parts copper powdered as described in Specification 506,432 is added to the ball mill and grinding continued for about ¢ to 1 hour. The product is washed with water and the resulting suspension coagulated by addition of sulphuric acid to produce a solution of about 0À5 per cent strength. The coagulated powder is then washed by elutriation with 0À5 per cent sulphuric acid and then with water and finally dried. For making a powder comprising equal parts of silver, copper and zinc, the powdered brittle alloy consists of copper and zinc to which a fine powder of silver is added. For a powder containing 20 parts tin, 56 parts silver and 24 parts copper, the powdered brittle alloy consists of 20 parts tin, 24 parts copper and 16 parts silver, to which 40 parts of powdered silver are subsequently added. For a powder of 80 parts copper, 15 parts silver, and 5 parts phosphorus, the powdered brittle alloy consists of 50 parts commercial 10 per cent phosphor-copper, and the malleable powdered alloy consists of 35.parts of copper and 15 parts of silver. For making a powder containing 37À5 parts gold, 20 parts cadmium, 3 parts zinc, 21À5 parts silver and 18 parts copper, the powdered brittle alloy consists of 20 parts cadmium, 3 parts zinc, 18 parts copper and 7 parts silver, and the powdered malleable alloy of 37À5 parts gold and 14À5 parts silver. Fluxes may be mixed with the powders.